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Fast idle wax unit replacement

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The cooler temps are upon us and my bike now struggles to reach fast idle, it can take up to a minute to settle. Is that the telltale of a failing wax unit? Last year I removed the airbox to inspect my vacuum lines and found the rubber seal that's around the wax unit rod to be torn, though it operates its full range of motion.

 

Provided a new unit is on the way, what's the procedure to adjust the nut on the rod? I see that this part was adjusted at the factory when assembling the bike and shouldn't be messed with, but what about a new part?

 

Thanks,

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Before you blame the wax-core warm up unit as the (sole) cause for your bike's poor start-from-cold you should ask yourself: Have the non-VTEC valve clearances ever been checked/adjusted?  Tight non-VTEC valve clearances can cause poor starting characteristics.  What is the condition of the spark plugs?  Are they original to the bike?  Old spark plugs that are in the last half of their useful lifespan can cause poor starting characteristics.   

 

As part of my refurbishment efforts on my '01 VFR800 I replaced the fast-idle wax-core unit, just opened up the assembly that the unit goes inside of, removed the old unit, installed the new one and put things back together.  No need to change any of the factory "white paint" marked items.

 

Yeah, wax-core units don't live forever, they slowly lose their original range of motion, there's a lot of variation in longevity with something like a wax-core unit, some individual examples come off the production line at the high quality end of the spectrum and they last longer than others produced right along with the good ones, but there's a reasonable lifespan you can expect from this sort of thing and it seems like 20 years is "great" and slightly less is "good" and less than that is "fair".  But whatever, the wax-core unit isn't hard to replace.

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Also make sure that the orifice on the top of the thermostat housing that supplies the coolant to the wax unit is not blocked.

It is small, and because it sits on top it often fills with gunk if any air has been in the cooling system. 

It happened to mine and also my mates Blackbird. 

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The spark plugs are new from last year, they were in bad shape and replacing them literally transformed the bike.

 

Is there any benefit in first changing the coolant? It is on my to-do-list as I haven't changed it in years, perhaps it's worth doing that before messing with the wax unit.

 

With regards to the core itself, is it a separate part from the whole assembly part number 16044-MCW-003?

 

Thanks guys,

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If the bike is "struggling to reach fast idle" when first started then I doubt you have any coolant flow issue. When the bike is cold the wax unit will also be cold, and at that time is will be in it's cold extended position. If there was any coolant blockage the unit would be slow to reduce the fast idle back to a normal warm speed. I would be taking a look at the wax unit and the movement of the starter valves to ensure that the starter valves are being held open when cold. If the starter valves themselves are out of whack that won't be helping. 

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3 hours ago, Terry said:

If the bike is "struggling to reach fast idle" when first started then I doubt you have any coolant flow issue. When the bike is cold the wax unit will also be cold, and at that time is will be in it's cold extended position. If there was any coolant blockage the unit would be slow to reduce the fast idle back to a normal warm speed. I would be taking a look at the wax unit and the movement of the starter valves to ensure that the starter valves are being held open when cold. If the starter valves themselves are out of whack that won't be helping. 

Terry, doesn't the wax core expand when heated, and contract when cold?

 

Unless you're skipping part that in your explanation and jumping forward to the part where the contracted wax core pulls on the starter valve control mechanism which holds it open, and when the wax core warms and expands it relaxes its pulling on the mechanism.  

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11 minutes ago, GreginDenver said:

Terry, doesn't the wax core expand when heated, and contract when cold?

Actually Greg you are probably correct but the manual is not that easy to figure. Looks like the WU connects and pulls the SV open for cold, then releases them for hot, so shorter cold/longer hot seems more likely from closer inspection. The key in any case is to check whether the SV's are being lifted when cold and set down when hot, which is easy enough to visually spot.

 

image.thumb.png.5655b70efd66aa0e9d2768d968e38ab4.png

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You're actually right Terry, The problem with mine and my mates was high idle after getting hot. Not slow idle while cold.

I've also noticed US bikes seem to have a lot more corrosion than Oz bikes.

Not much rain here, and definetly no salt in winter.

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6 hours ago, Terry said:

Actually Greg you are probably correct but the manual is not that easy to figure. Looks like the WU connects and pulls the SV open for cold, then releases them for hot, so shorter cold/longer hot seems more likely from closer inspection. The key in any case is to check whether the SV's are being lifted when cold and set down when hot, which is easy enough to visually spot.

 

image.thumb.png.5655b70efd66aa0e9d2768d968e38ab4.png

Here's a short video somebody made explaining the wax unit on a 6th Gen VFR:

https://www.youtube.com/watch?v=k4oVVbzTvVo

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The whole thing is just goofy in my opinion. Instead of adding a couple lines of code to their ECU, they add two coolant hoses and a wax actuator.

 

I capped the nipples supplying water to mine and installed a manual choke cable which is virtually unnecessary in warm weather. 

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